A study will be made of the physical, chemical, and biochemical mechanisms of interaction between proteolytic enzymes and naturally occurring protein inhibitors in proteolytic enzymes. Inhibitors and enzymes of differing physical and chemical properties and different specificities will be used. The enzymes will include: trypsin, alpha-chymotrypsin, and subtilisin. The inhibitors will include: avian ovomucoids, avian ovoinhibitors, Kunitz pancreatic inhibitor, and human serum alpha1-trypsin inhibitor. The interactions will be characterized by physical and chemical methods including ultra-centrifugation, gel electrophoresis and filtration, and other similar methods. Chemical modification of the structures of the enzymes and the inhibitors will be a primary tool. In particular, the roles of disulfides will be studied.